Polishing process



United States Patent 3,321,873 PULISHING PROCESS Newton G. Leveskis, 49 Vallecito Laue, Walnut Creek, Calif. 94596 No Drawing. Filed Apr. 5, 1965, Ser. No. 445,764 13 Claims. (Cl. 51-316) This application is a continuation-in-part of copending application Ser. No. 357,309, filed Apr. 3, 1964, now abandoned.

This invention relates to an improved process for grinding and polishing assorted objects such as rocks. More particularly, it relates to the use of novel materials that are added to the solution used during at least the polishing stage of such a process.

The grinding and polishing of rocks and similar materials for purposes of creating a more esthetically appealing end product is well known. In general, the process has been carried out by placing the objects in a device suitable for tumbling the objects which may take the form of a barrel or drum. The items to be ground and polished are placed in the tumbler and a water solution is added to cover them. A grinding charge is added to the water, for example, silicon carbide, and the entire mixture is tumbled constantly for a considerable period of time extending frequently for many days. Solutions are changed periodically to place fresh water and grinding materials that are less coarse in contact with the objects to be processed, working up to a pre-polish charge and finally a polishing charge.

At least during the final polishing stage, it has become the practice to increase the viscosity of the liquid used in the tumbler. It is understood by those skilled in the art that this viscosity increase is important in order to obtain the desired action by the polishing chemical. The assumption has been that simply by increasing the viscosity of the tumbler liquid the desired high polish was obtained.

It has been the practice to add various materials to the polishing solution to obtain this viscosity increase including such items as sugar, detergents, soaps, sawdust, oatmeal, and rice hulls. All of these materials have serious drawbacks for one reason or another. In most cases they are quite messy to use and in some cases create a substantial increase in cost in practicing the process. In some cases they may even be deleterious to the tumbling apparatus. For example, where the tumbler or barrel employed has a rubber liner, the use of certain liquid detergents may have an adverse elfect upon them.

In accordance with the present invention it has now been discovered that the viscosity of the solution containing the polishing charge can be suitably increased by the requisite amount by adding thereto a suitable amount of certain water soluble polymers, for example a high molecular weight polyacrylamide polymer. While accomplishing the desired viscosity increase, the present materials avoid the undesired mess, cost and possible deleterious aspects of all of the materials heretofore employed.

The present invention has another even more significant advantageous aspect. Aside from the above benefits obtained through its use, the present materials provide a materially enhanced luster and polished appearance in the end products than has been obtained with the use of any of the prior art materials. As will be shown hereinafter in the specific examples illustrating the present invention, the objects processed in accordance with the present invention show an increased luster that is easily measurable in terms of light reflectance from the surfaces thereof, and differs in kind from the light reflection obtained from surface of objects polished without benefit of the present additives.

3,3ZL873 Patented May 30, 1967 ICC It has also been discovered that the final polishing charge of fine abrasive can be entirely eliminated and the polished condition obtained in a solution containing only a polymer of the present invention. It is believed that the polymer creates a solution of a viscosity that permits just enough object contact to cause a burnishing and polishing effect while eliminating more severe contact which might cause damage due to hammering during such contact. Of course the polishing chemical can still be used if desirable and in general will be used in the easly stages of grinding and pre-polish.

Suitable polymers for the present process include all water soluble polymers capable of creating a sol state aqueous solution at a 2% polymer concentration having a viscosity above about 10,000 centipoises at 2025 C. The polymer may technically be dispersed in colloidal suspension and not be dissolved. The term water soluble is used broadly to include such media. All polymers developing a viscosity over about 10,000 centipoises and short of the gel state under the temperature and concentration conditions noted are satisfactory for present purposes. Typical examples of commercially available products include Union Carbide Corporations hydroxyethyl celluloses known as Cellosize QP-15,000, QP-30,000, and QP-50,000 and Stein, Hall 8; Co., Inc.s Polymer 705-D- 163, Polymer 705DA, and Polymer 705DB which are polysaccharides. Polymers creating less viscosity than the amount noted do not provide the desired polished surfaces.

The polymer should be added to at least the final polish step of the process. However, there may be instances where it is desirable and beneficial if the polymer is added also to solutions utilized in the earlier stages of the process such as during the grinding and prepolish steps.

A group of materials giving excellent results in the present process are generally referred to as high molecular weight polyacrylamide polymers. In preferred embodiments these materials may suitably be selected from polymers having either of the following approximate general formulas:

POLYMER A POLYMER B CH2 3 L Na+ n groups but even so the material contains an overwhelming.

preponderance of amide functional groups. Suitable materials of this type have been determined to have a molecular weight on the order of about one million.

With respect to the polymer B shown above, it is noted that the material contains approximately amide functional groups and 25% carboxyl groups. Therefore, this material may be said to have a minor proportion of carboxyl groups, i.e., less than 50% with respect to the major proportions or proportion of amide functional groups. Because of the carboxyl groups, this type of material is classi-fied as an anionic polyelectrolyte in neutral and alkaline solutions. Under acid conditions the ionization is repressed and the polymer assumes a nonionic character. Suitable materials of this type have been esti- 3,3 3 mated to have a molecular weight on the order of about two to three million.

With respect to the molecular weight of polymer B and polymer A it should be appreciated that molecular weight determinations are only approximate and that suitable materials may have molecular weights which differ substantially from those here recited.

The polyacrylamide polymers within the scope of the present invention are utilized to increase the viscosity of the grinding and polishing solutions. These solutions are generally aqueous in nature, and it has been found that the pH of the solution has an effect upon the viscosity of solutions to which the polyacrylamide polymers have been added. In general, highly acid solutions are less the other side of the tumbler, hereinafter referred to as side B, received no additive. The polymer utilized is known commercially as Separan AP3O manufactured by Dow Chemical Company which is a polymer having a molecular weight of about two to three million and containing both amide and carboxyl groups in the ratio of about 3 to one respectively. The tumbler was operated for 12 days. After tumbling, the contents of side A weighed 4 pounds 7 02., whereas the contents of side B weighed 4 pounds 2 oz.

The glass chip contents from both sides of the tumbler were then washed with water until the water was clear. The chips were replaced in their respective sides of the tumbler. To each side of the tumbler there were added viscous than the more neutral or alkaline ones. Optimum one-half pound (600-grit size) silicon carbide, one quart results can therefore be obtained with the polyacrylarnide of water. To side A (4 pounds of 7-02. glass chips) there materials if buffers are added to the solution as required were again added 2 grams of the same polyacrylamide so as to maintain the pH of the solutions above about 5. polymer. The tumbler was operated for four days. The In practicing the present invention, the selected pOlishweight following tumbling for the contents of side A was ing polymer is added to the solution containing the ob- 4 pounds 3 oz. and for side B was 3 pounds 5 02. All of jects to be polished in an amount sufficient to increase the the contents were then washed with water until the wash luster or light reflectance of the surfaces of these objects. water was clear. The amount permits contact for burnishing without ham- The contents were then replaced in their respective mering. It should me made clear that the precise amount sides of the tumbler. To each of the tumbler sides there utilized will vary depending upon the material being procwere added 1 quart of water and /2 pound of iron oxide essed and the particular eflect desired. Experience to date (polishing grade). To side A only 6 grams of the same has shown that the addition of about 1 to 15 grams of the polyacrylamide polymer were added. The tumbler was polymer for each quart of solution, which is generally again operated for ten days. A piece of glass was rewater, will achieve the desired result. Best results are obmoved from each side every day during this latter tentained between about 3 and 10 grams per quart. Where day period. The amount of transmitted light was measthe addition greatly exceeds the upper 15 gram limit, it ured using a Precise volt ohmmeter in combination with will generally be found that the solutions become una cadmium sulfide photoelectric cell (Polaris MA]1). desirable for practical purposes because of their excessive- A small bulb was used as a light source having 60 milly high viscosity which probably prohibits suificient oblilumens output with a voltage of 1.5 volts and a current ject contact. The use of less than the lower limit of 1 gram of 15 milliamps, The following daily ohm resistances were may result in insufficient viscosity increase to achieve the observed.

1 2 3 i 4 5 6 7 i s 9 10 A, Ohms 10. art 9.2K 8.5K 7.3K 7.1K 7.0K a 8K 6.8K 6.7K 6.7K 13, Ohms 10. 6X 10.3K 10,11; 10. OK 10.0K 9.9K 9.9K 9.9K 9.8K 9 8K 1 A: Glass from side A 01' the tumbler. 2 B: Glass from side B of the tumbler.

desired polished effect, probably due to excessive contact or hammering which can be seen on the object as a pitted appearance and which may show up as crescent shaped marks under a microscope.

The present process is applicable to any suitable hard object which generally has plural and irregular surfaces that can be enhanced by the present type of polishing and grinding process. Frequently, these material will be rocks, although the process is equally applicable to other items such as plastic objects, glass objects, which may be obtained from ordinary broken glass, for example, as well as metal objects.

The abrasive grinding and polishing chemical or charge, when utilized in the present process, is consonant with those generally used in the past and may include such materials as tin oxide, iron oxide, ceric oxide, and the like.

To illustrate the present invention and'the improved results obtained therefrom, the following examples are offered.

Example 1 A double compartment tumbler (Scott-Murray 10 lb. capacity) was utilized. Five pounds of broken bottles were added to each side of the tumbler. In addition, there were added to each side of the tumbler one-half pound (320-grit size) silicon carbide and one quart of water. On one side, hereinafter referred to as side A, there were added tWo grams of polyacrylamide polymer, while Example 2 In the same two sided tumbler 5 pounds of broken obsidian chips which had previously been taken to the pro-polish stage were added to each side of the tumbler. Also added to each side was one-half pound of tin oxide polishing grade. To side A only there were added 5 grams of the same polymer utilized in Example 1. One quart of water was added to side A and the solution had a viscosity of about 1,000 cps. To side B of the tumbler there was added one quart of sugar water having a viscosity of 1,000 cps. measured with a Brookfield viscometer.

The tumbler was operated for 10 days and a maximum reflection read on the contents from each side of the tumbler in a Precise volt ohmmeter using a cadmium sulfide photo cell and a small light source. A maximum reading was obtained'by turning the obsidian chips to the,

Example 3 This example was conducted in the same manner as Example 2 except that a mixture of rocks was used comprising /3 obsidian, petrified Oregon wood, and /3 carnelian from India. This rock mixture was taken through the pre-polish stage and then treated as follows. In side A of the tumbler were placed pounds of the rock, one quart of water, 30 grams of polyacrylamide polymer and /2 pound iron oxide polishing grade. The polymer is commercially known as Separan NPlO sold by Dow Chemical Company and is a non-ionic polymer having a preponderance of amide groups and a molecular weight of about 1 million. In side B of the tumble-r there were placed 5 pounds of rock, one quart of water, two cups of Tide household detergent, and one-half pound of iron oxide polishing grade. The tumbler was operated for days and inspected.

In side A all of the stones were bright and polished. In side B only the carnelian was bright and polished.

Example 4 This example was run similarly to Example 3, except that broken glass which had previously been taken through the pre-polishing stage was used. In side A of the tumbler 5 pounds of the glass, 1 quart of water, 7 grams of the polymer of Example 3, and /2 pound of ceric oxide were added. In side B of the tumbler 5 pounds of glass, one quart of water and sugar adjusted so that the viscosity of the solution was about the same as that in side A was added. The tumbler was operated for six days The amount of reflectance was read on a Precise volt ohmmeter using a cadmium sulfide photo cell and a small light source. The daily readings in ohms from the contents of each side of the tumbler were as follows.

Again, the lower resistance indicates the higher reflectance illustrating the significantly higher polishing obtained with polyacrylamide polymers of the present invention.

Examples 6 and 7 to follow illustrate the invention in relation to suitable types of water soluble polymers other than the polyacrylamide type. These two examples also illustrate the surprising result obtained by this invention by way of a final polished eflect in the absence of the abrasive charges previously used in the final polishing solution.

In all of the following experiments the same type of double compartment tumbler described in the foregoing examples was utilized.

Example 6 To each side of the tumbler five pounds of Apache tears (volcanic obsidian) was added for each trial which had already been taken to the prepolished stage. One quart of water was placed in each side of the tumbler. On one side of the tumbler there was added in successive trials a number of different polymers to be tested for their polishing efficiency. The other side of the tumbler was used as a control and contained no additives. The results are tabulated below in terms of ohm readings as a measure of the reflectivity of the polished items as described in the previous examples.

Viscosity (cps, Amount Time Reflec- Type of Polymer 25 C.) of 2 0 of Run, tivity Appearance Solution Polymer, days (ohms) gms.

Control None 6 105K Knock marks, irregular surface. Cellosize 1 hydroxyl ethyl cellulose QP-300. 225-325 6 6 100K Do. Cellosize QP-4400 6, 000 6 6 77K Part polished, some knock marks. Cellosize QP-15, 000- 18. 000 6 6 29K Lustrous polish. Cellosize QP-30, 000 35, 000 6 6 K Do. Cellosize QP-50, 000- 55, 000 6 0 36K Do. Polymer 2 705-D l63. 40, 000 6 6 35K Do. Polymer 705D-A 13, 000 6 6 33K Do. Polymer 705-D-B 8, 000 6 6 70K Some knock marks. Sugar l 6 6 100K Knock marks, irregular surface.

1 Cellosize polymers are hydroxyethyl cellulose materials available from Union Carbide Corporation. 2 The Polymer 705 materials are a group of polysaccharlde materials available from Stein, I-Iall dz 00., Inc.

and inspected. The glass in side A was significantly more highly polished than the glass in side B of the tumbler.

Example 5 Using the same two-sided tumbler, 7 pounds of metal stampings were added to each side thereof. To side A of the tumbler there were also added 2 grams of the polymer used in Example 1, one quart of water and A2 pound of silicon carbide (GOO-grit size). To side B of the tumbler there were also added /2 pound of the same silicon carbide and 1 quart of water. The tumbler was operated for three days and the silicon carbide was washed away from the contents of each side of the tumbler. To the contents of side A there were then added 6 grams of the same polymer, 1 quart of water and A2 pound of tin oxide. To side B of the tumbler there were added /2 pound tin oxide and 1 quart of water.

Over a three-day period while the tumbler was in operation samples were taken from each side thereof.

Example 7 This experiment was conducted in the same manner as Example 6 utilizing the double tumbler except that iron stampings which had been brought to the prepolished state were utilized instead of Apache tears. The following results were obtained.

Viscosity Amount of Time Reflec- Type of polymer (cps, C.) Polymer, Run, tivity Appearance of 2% Solution gins. hrs. (ohms) Control 4 24 40K Dull. Ccllosize hydroxycthyl cellulose QP-300.. 300 4 24 40K Do. Cellosize QP 4400. 6, 000 4 24 39K Do. Ccllosize QP-15,000 18, 000 4 24 25K Bright, shining. Clelosize QP30,000 i5, 000 4 24 26K D0. Cellosize (JR-50,000.. 55, 000 4 24 25K Do. Polymer 705-D-163 40, 000 4 24 23K Do. Polymer 705-D-A 13, 000 4 '24 25K Do. Polymer 705'DB 8, 000 4 24 34K Slightly (lull. Sugar sucrose 1 4 24 40K Dull. Sodium dodecyl benzene sulionate l 4 24 40K Do.

Example 8 Weight Time, Amount, Type of Polymer Loss, days gms.

gms.

Control 45 2 2 Cellosize QP-300. 43 2 2 Cellosize QP50,000 10 2 2 Sugar. 40 2 2 Polymer 705-D-163 12 2 2 Sodium dodecyl benzene sulfonate 43 2 2 From the above it can be seen that significant loss of product occurred in all cases except where a polymer of the type required in the present process was employed for increasing the viscosity of the solution. Thus, only in the case of the Cellosize QP50,000 and Polymer 7 05-D- 163 were Weight losses kept to a minimum. In all of the other cases a substantial portion of the products is lost during the polishing. This advantage of the present process is in addition to the polished appearance provided thereby.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be practiced within the spirit of the invention as limited only by the scope of the appended claims.

What is claimed is:

1. An improved grinding and polishing process for groups of objects such as rocks having plural and irregular surfaces comprising tumbling said groups of objects in successive aqueous solutions containing grinding and polishing charges for preselected periods of time, at least the final polishing solution containing about 1 to 15 grams per quart of Water of a polyacrylamide polymer having the approximate general formula per quart of water of a polyacrylamide polymer having the approximate general formula ll all and having a molecular weight on the order of about 2 to 3 million.

3. An improved process in accordance with claim 1 wherein a buffer is added as required to solutions containing said polymer so as to maintain a pH above about 5 therein.

4. An improved process in accordance with claim 2 wherein a buffer is added as required to solutions containing said polymer to maintain the pH above about 5 therein.

5. In the process for finish-polishing objects having relatively hard surfaces including rocks, pieces of metal, glass, and plastic, the improvement comprising the step of: moving a plurality of like objects of the above type to cause random contact therebetween until polished in an aqueous solution containing a water soluble polymer at a concentration low enough for sufficient contact between objects for the polishing thereof but high enough to avoid damage to the surfaces of the objects from the impact upon such contact, said polymer being capable of developing a viscosity in aqueous solution at a concentration of 2% and 2025 C. above about 10,000 centipoises but less than a gel state.

6. An improved grinding and polishing process for groups of like objects such as rocks having plural and irregular surfaces comprising tumbling a group of said objects in successive aqueous solutions containing grinding and polishing charges for preselected periods of time, at least the final polishing solution containing about 1-15 grams per quart of water of a water soluble polymer selected from polymers capable of creating a sol state aqueous solution at 2% polymer concentration of a viscosity above about 10,000 centipoises at 2025 C.

7. A process in accordance with claim 6 wherein said polymer is present at a concentration of about 3-10 grams per quart of water in the final polishing solution.

8. A process in accordance with claim 6 wherein said final polishing solution contains an abrasive polishing charge in addition to said polymer.

9. An improved grinding and polishing .process for groups of objects such as rocks having plural and irregular surfaces comprising tumbling groups of like objects in successive aqueous solutions containing grinding and polishing charges for preselected periods of time, and then tumbling the objects in a final polishing solution consisting essentially of water containing about 3-10 grams per quart of a water soluble polymer selected from polymers capable of creating a sol state aqueous solution at 2% polymer concentration having a viscosity above 10,000 centipoises at 20-25 C., said final polishing solution being free from an abrasive polishing charge.

10. A process in accordance with claim 5 wherein said polymer is a high molecular weight polyacryarnide.

11. A process in accordance with claim 10 wherein said high molecular weight polyacrylamide has the approximate general formula ll 5323M hall where X is an integer from 0 to 1, and n is an integer selected to provide a polymer having a molecular weight on the order of about 1 million when X=0 and a molecular weight on the order of about 2 to 3 million when X=1.

12. An improved process in accordance with claim 6 References Cited UNITED STATES PATENTS 2,540,003 1/1951 McCoy 51-316 3,071,456 1/1963 Cheesman 51316 FOREIGN PATENTS 142,978 5/ 1949 Australia. 650,685 10/ 1962 Canada.

LESTER M. SWINGLE, Primary Examiner. 

6. AN IMPROVED GRINDING AND POLISHING PROCESS FOR GROUPS OF LIKE OBJECTS SUCH AS ROCKS HAVING PLURAL AND IRREGULAR SURFACES COMPRISING TUMBLING A GROUP OF SAID OBJECTS IN SUCCESSIVE AQUEOUS SOLUTIONS CONTAINING GRINDING AND POLISHING CHARGES FOR PRESELECTED PERIODS OF TIME, AT LEAST THE FINAL POLISHING SOLUTION CONTAINING ABOUT 1-15 GRAMS PER QUART OF WATER OF A WATER SOLUBLE POLYMER SELECTGED FROM POLYMERS CAPABLE OF CREATING A SOL STATE AQUEOUS SOLUTION AT 2% POLYMER CONCENTRATION OF A VISCOSITY ABOVE ABOUT 10,000 CENTIPOISES AT 20*-25*C. 